Centrifugal radial turbine

ABSTRACT

A centrifugal radial turbine includes at least one support disc having a first face bearing at least one radial rotor stage formed by an array of blades arranged in succession along a respective circular path. The disc has through induction channels situated in a position radially external with respect to a respective shaft and radially internal with respect to the radial rotor stage. At the respective through induction channels, the disc includes a plurality of induction rotor blades of at least one respective axial rotor stage.

FIELD OF THE FINDING

The subject of the present invention is a centrifugal radial turbine for producing electrical and/or mechanical energy. The present invention is situated in the field of those processes that provide for the obtainment of one or more phases of expansion of a work fluid through one or more turbines adapted to convert the energy of the fluid by means of the expansion thereof in the turbine(s). Preferably but not exclusively, the present invention refers to the centrifugal radial expansion turbines of counter-rotating type. Preferably but not exclusively, the present invention refers to the expansion turbines used in the apparatuses for producing energy by means of steam Rankine cycle or organic Rankine cycle (ORC). In the ORC apparatuses, work fluids of organic type are used in place of the conventional water/steam system.

BACKGROUND OF THE FINDING

Centrifugal radial turbines are known that are used for the expansion of steam or organic fluids.

For example, the public document WO 2013/108099 illustrates a turbine for the expansion of an organic fluid in a Rankine cycle provided with arrays of rotor and stator blades that are alternated in a radial direction. The supply of the steam in the turbine is obtained in frontal direction. In a first section of the turbine, defined at high pressure, a first expansion of the work fluid is provided in a substantially radial direction. In a second section, defined at low pressure, a second expansion of the work fluid is provided in a substantially axial direction. The stator blades are supported by an external casing of the turbine.

Counter-rotating centrifugal radial turbines have also been known for a long time, which are used for the expansion of the water steam.

For example, the public document GB 311,586 illustrates a steam turbine that comprises two opposite rotating discs bearing blade rings. In proximity to the radially more internal blade ring, passages are present that traverse the discs starting from steam chambers obtained in the turbine containment box. Steam induction pipes are connected to said chambers.

Also known are counter-rotating centrifugal radial turbines in which the induction of the steam between the discs occurs through ducts obtained in the rotation shafts integral with said discs.

SUMMARY

In such context, the Applicant has observed that the known centrifugal radial turbines, like those described above, can be improved with regard to various aspects, in particular in a manner so as to increase the efficiency thereof and simultaneously improve the structural strength thereof.

The Applicant first of all observed that the induction passages obtained in the discs, for example those described in the abovementioned document GB 311,586, first cause a structural weakening of the discs themselves. Indeed, such passages must be sized in a manner such to allow the transit of the maximum fluid flow rate that the turbine can treat, so as to maximize the efficiency thereof. In order to limit the load losses through said passages, the passage crossing speed cannot however exceed specific values (approximately 10 m/s), so that it is necessary and known to obtain said passages with areas such to obtain the desired flow rate even with low crossing speeds.

The Applicant also observed that the fact that such passages rotate with the respective disc still causes—even if limiting the crossing speeds as mentioned above—considerable load losses that negatively affect the efficiency of the entire turbine.

The Applicant also observed that the centrifugal radial turbines with (non counter-rotating) stator and rotor blades, like those described in the document WO 2013/108099, in particular in the configurations of FIG. 1 and FIG. 2, have considerable problems relative to the insertion of the work fluid, since spaces are limited on the side of the machine where there is the support shaft; in addition, in such zone overly high temperatures cannot be allowed (cooling problems) in order to avoid damaging delicate components such as the mechanical seal and the bearings that normally equip said machines and said areas.

In such context, the Applicant set the objective of proposing a centrifugal radial turbine, preferably but not exclusively counter-rotating, with improved efficiency with respect to the centrifugal radial turbines, counter-rotating and otherwise, of the prior art.

More generally, the Applicant has set at least one of the following objects/improvements with regard to the prior art:

-   -   improving the efficiency of the phase of induction of the work         fluid between the rotor and stator blades (in the case of         single-disc centrifugal radial turbines) or between the rotor         discs (for counter-rotating centrifugal radial turbines);     -   increasing the structural strength of the disc or discs;     -   simplifying the induction of the work fluid even with high flow         rates, as in the case of expansion of organic fluids in ORC         cycles;     -   allowing the use of the turbine, in particular counter-rotating,         with any work fluid (e.g. organic fluids or water).

The Applicant has found that the indicated objective, at least one of the above-listed objects and still others can be achieved by also exploiting the induction phase in order to rotate the disc or discs by means of an axial stage obtained at the induction passages of said disc or said discs or, in other words, shaping said passages in a manner so as to have a blading.

In particular, the indicated objectives, at least one of the above-listed objects and still others are substantially achieved by a centrifugal radial turbine according to one or more of the set of claims.

Aspects of the invention are illustrated hereinbelow.

According to one aspect, the present invention regards a centrifugal radial turbine, comprising:

a fixed containment case;

at least one support disc having a first face bearing at least one radial rotor stage formed by an array of blades arranged in succession along a respective circular path;

at least one rotation shaft integral with the respective disc;

in which said at least one radial rotor stage is situated in an expansion volume for a work fluid;

in which said at least one disc has through induction channels situated in radially external position with respect to the respective shaft and radially internal position with respect to said at least one radial rotor stage;

in which said at least one disc is free to rotate together with the respective shaft around a rotation axis under the action of the work fluid entering through the through induction channels;

characterized in that, at the respective through induction channels, said at least one disc comprises a plurality of induction rotor blades of at least one respective axial rotor stage.

According to one aspect, the present invention regards a centrifugal radial turbine, comprising:

a fixed containment case;

a support disc having a first face bearing at least one radial rotor stage formed by an array of blades arranged in succession along a respective circular path; a rotation shaft integral with the respective disc;

at least one radial stator stage fixed with respect to the containment case and formed by an array of blades arranged in succession along a respective circular path and in a radially external and/or radially internal position with respect to said at least one radial rotor stage,

in which an expansion volume is delimited between the support disc and the containment case;

in which said at least one disc has through induction channels situated in radially external position with respect to the respective shaft and radially internal position with respect to said at least one radial rotor stage;

in which said at least one disc is free to rotate together with the respective shaft around a rotation axis under the action of the work fluid entering through the through induction channels;

characterized in that, at the respective through induction channels, said at least one disc comprises a plurality of induction rotor blades of at least one respective axial rotor stage.

According to one aspect, the present invention regards a counter-rotating centrifugal radial turbine, comprising:

a first support disc having a first face bearing at least one radial rotor stage formed by an array of blades arranged in succession along a respective circular path and with a first orientation;

a first rotation shaft integral with the first disc;

a second support disc comprising a first face bearing at least one radial rotor stage formed by an array of blades arranged in succession along a respective circular path and with a second orientation, opposite the first;

a second rotation shaft integral with the second disc;

in which the first disc faces the second disc in order to delimit an expansion volume and the blades of the first disc are radially alternated with the blades of the second disc;

in which each of the discs has through induction channels situated in radially external position with respect to the respective shaft and radially internal position with respect to the arrays of blades of the radial rotor stages;

in which the first and the second disc are free to rotate together with the respective shafts around a common rotation axis and rotate in opposite directions under the action of a work fluid entering through the induction channels;

characterized in that, at the respective through induction channels, each of the discs comprises a plurality of induction rotor blades of at least one respective axial rotor stage.

The induction channels are opened both on the first and on a second face opposite the first of the disc(s) and are preferably extended along an axial direction.

The rotor blades each have a leading edge (and a trailing edge) that is extended along a substantially radial direction. The leading edge faces the second face of the respective disc. The trailing edge faces the first face of the respective disc.

The inlet of the work fluid into the expansion volume (comprised between the disc and the case or between the first and the second disc if counter-rotating) occurs through the induction channels situated at a radially internal portion of said disc(s). The fluid is moved, expanding outward, away from the rotation axis, and exits at a radially peripheral portion of the abovementioned disc(s).

In one aspect, the induction channels are at least partially delimited by said induction rotor blades.

In one aspect, the adjacent induction channels are separated by one of said induction rotor blades.

In one aspect, the induction channels and the induction rotor blades are arranged in succession along at least one circular path coaxial with the rotation axis.

In a preferred embodiment, the axial rotor stage comprises a plurality of rotor blades arranged one after the other in an annular passage (which is extended along said circular path) obtained in the disc and coaxial with the rotation axis and said rotor blades divide said annular passage into a plurality of the abovementioned induction channels.

The Applicant has verified that the solution according to the invention allows introducing the steam by means of an axial expansion stage that allows carrying out such process in an efficient manner and with much more limited passage channels on the disc(s) with respect to those of the prior art.

In one aspect, the induction rotor blades are integrally obtained in the respective support disc. This ensures greater solidity and structural strength of the disc(s).

In one aspect, the disc(s) and the relative rotor blades are obtained by means of three-dimensional sintering techniques (method for creating objects from metal and/or ceramic powders). This allows obtaining the disc(s) and the rotor blades with limited size, suitable for low-power applications (e.g. for powers comprised between about 5 kW and about 50 kW), for example in the automotive field.

In one aspect, the ratio between the radial height of each induction rotor blade and the diameter of the support disc(s) is comprised between about 0.007 and about 0.05.

With radial height it is intended the extension along a radial direction of an induction rotor blade. With diameter of the disc it is intended the maximum diameter of the disc excluding possible auxiliary blades of an auxiliary axial stage arranged on a periphery of said disc.

The rotor blades and consequently the passage channels are small with respect to the size of the disc(s) and consequently the disc/discs is/are more solid with respect to those of the prior art.

In one aspect, an axial traversing speed of the work fluid through the induction channels is comprised between about 35 m/s and about 100 m/s, preferably between about 40 m/s and about 45 m/s. Due to the presence of the rotor blades, the speed of crossing the induction channels is such that the necessary flow rates are obtained with passage areas that are reduced with respect to the prior art.

In one aspect, the turbine comprises a plurality of induction stator blades of a respective axial stator stage side-by-side the induction rotor blades of the support disc or of each of the support discs and arranged on the side of the second face of the respective support disc opposite the first face. The axial stator stage together with the respective axial rotor stage define an axial induction stage.

In one aspect, the turbine comprises a fixed portion provided with a plurality of fixed induction openings side-by-side the induction rotor blades of the support disc or of each of the support discs and placed on the side of a second face of the respective support disc opposite the first face.

The fixed induction openings are in fluid communication with an inlet duct and, possibly, with an induction chamber arranged on one side of the fixed portion opposite the respective disc.

In one aspect, the induction stator blades delimit the fixed induction openings.

In one aspect, the induction stator blades are housed in the fixed induction openings.

In one aspect, each of the fixed induction openings houses at least one induction stator blade.

In one embodiment, the axial stator stage comprises a plurality of stator blades arranged one after the other in an annular passage obtained in the fixed portion and coaxial with the rotation axis of the disc or of the discs and said stator blades divide said annular passage into a plurality of the abovementioned fixed induction openings.

In one embodiment, the fixed induction openings are through holes or slots obtained in the fixed portion and each of said holes or slots houses one or more of the induction stator blades.

In one aspect, the axial rotor stage is of action type. The static pressure of the fluid upstream and downstream of the rotor blades is therefore the same.

In one aspect, the axial rotor stage is of reaction type.

In one aspect, the support disc or discs have compensation through openings obtained in radially internal positions with respect to the through induction channels, in order to balance the axial thrust on the discs.

In one aspect, the turbine comprises an annular chamber that is concentric and facing the second face of the support disc or of each support disc.

In one aspect, the fixed containment case that houses the support disc or discs comprises annular walls coaxial with the rotation axis and delimiting said annular chamber(s). The annular chamber is partly delimited by the support disc, partly by said annular walls and partly by further delimitation walls integral with (or in any case fixed with respect to) the containment case and facing the respective support disc.

In one aspect, each support disc comprises annular appendages projecting from the respective second face, coaxial with the rotation axis and sealingly engaged with the annular walls in order to delimit said annular chamber(s).

In one aspect, the turbine comprises a plurality of sliding gaskets, each interposed between one end of an annular wall and the respective annular appendage.

In one aspect, said sliding gaskets are mounted on the ends of the annular walls and slide against said annular appendices.

In a different aspect, said sliding gaskets could be mounted on the annular appendices and slide against the ends of the annular walls.

In one aspect, the turbine comprises at least one auxiliary axial stage placed in a position radially external with respect to the support disc with respect to each of the support discs. Said at least one auxiliary axial stage is placed downstream of the radial rotor stages with respect to a direction of the flow of the work fluid.

In one aspect, said at least one auxiliary axial stage comprises a plurality of auxiliary rotor blades situated at or directly mounted on a peripheral edge of each of the support discs.

In one aspect, said at least one auxiliary axial stage comprises a plurality of auxiliary stator blades mounted fixed on a support element placed in a position radially external with respect to the support discs.

In one aspect, said support element is part of a radially external portion of the containment case.

In one aspect, each of the support discs has an auxiliary annular appendage projecting from the respective first face, coaxial with the rotation axis and placed in a position radially external with respect to the radial stages.

In one aspect, said annular appendage is sealingly engaged with a radially internal ring bearing radially internal ends of the auxiliary stator blades.

In one aspect, the turbine comprises a sliding gasket interposed between the radially internal ring and the respective annular appendage.

In one aspect, the turbine comprises a nose integral with the containment case and situated in the inlet duct.

In one aspect, the nose is placed on the side of a second face of the support disc opposite the first face.

In one aspect, the nose is part of the fixed portion provided with the fixed induction openings.

In one aspect, the fixed induction openings and, preferably, the induction stator blades are situated circumferentially around the nose.

In one aspect, the turbine is part of plants for the cogeneration of energy of Rankine cycle type which are closed-circuit (so that the work fluid remains in the circuit even during maintenance) and use organic fluids with high molecular weight.

In a different aspect, the turbine can be used in open-cycle or closed-cycle steam plants.

Further characteristics and advantages will be clearer from the detail description of preferred but not exclusive embodiments of a centrifugal radial turbine in accordance with the present invention.

DESCRIPTION OF THE DRAWINGS

Such description will be set forth hereinbelow with reference to the set of drawings, provided only as a non-limiting example, in which:

FIG. 1 is a half-section view along an axial plane of a centrifugal radial turbine according to a first embodiment of the present invention;

FIG. 2 is a half-section view along an axial plane of a centrifugal radial turbine according to a different embodiment of the present invention;

FIG. 3 is a front view of a support disc belonging to the turbines pursuant to FIG. 1 or 2;

FIG. 4 is a front view of a portion of the turbine of FIG. 1; and

FIG. 5 illustrates a detail of the turbine pursuant to FIG. 1 or 2.

DETAILED DESCRIPTION

With reference to FIG. 1, the reference number 1 indicates overall an expansion turbine of counter-rotating centrifugal radial type in accordance with the present invention.

The illustrated centrifugal radial turbine counter-rotating 1 can be used in apparatuses for generating mechanical and/or electrical energy, for example of organic Rankine cycle (ORC) type or steam Rankine cycle type. Preferably but not exclusively, the illustrated counter-rotating centrifugal radial turbine 1 is used in low-power applications (e.g. for generating powers comprised between about 5 kW and about 50 kW).

The turbine 1 comprises a fixed containment case 2 which at its interior houses a first support disc 3 and a second support disc 4. The support discs 3, 4 can freely rotate, each independently from the other, in the support case 2 around a common rotation axis “X-X”. For such purpose, the first disc 3 is integral with a respective first rotation shaft 5 mounted in the containment case 2 by means of first bearings 6. The second disc 4 is integral with a respective second rotation shaft 7 mounted in the containment case 2 by means of respective second bearings 8.

The first support disc 3 has a first face 9 that bears a plurality of radial rotor stages 10, 11, 12, 13 radially arranged in succession one after the other. Each of said radial rotor stages 10, 11, 12, 13 comprises a plurality of blades 14 arranged in an array along a circular path concentric with the rotation axis “X-X”. In other words, the circular arrays of blades of the different stages 10, 11, 12, 13 form concentric rings.

The second support disc 4 has a respective first face 15 that bears a plurality of radial rotor stages 16, 17, 18, 19 radially arranged in succession one after the other. Each of said radial rotor stages 16, 17, 18, 19 comprises a plurality of blades 20 arranged in an array along a circular path concentric with the rotation axis “X-X”. In other words, the circular arrays of blades of the different stages 16, 17, 18, 19 form concentric rings.

The first face 9 of the first support disc 3 is placed across from the first face 15 of the second support disc 4 and the blades 14 of the first disc 3 are radially alternated with the blades 20 of the second disc 4. In other words, the radial rotor stages 10, 11, 12, 13 of the first support disc 3 are alternated along radial directions with respect to the radial rotor stages 16, 17, 18, 19 of the second support disc 4. The blades 14 of the first support disc 3 terminate in proximity to the first face 15 of the second support disc 4 and the blades 20 of the second support disc 4 terminate in proximity to the first face 9 of the first support disc 3.

The leading edge and the trailing edge of each of the abovementioned blades 14, 20 of the radial rotor stages 10, 11, 12, 13, 16, 17, 18, 19 are extended substantially parallel to said rotation axis “X-X”, so that they are capable of working under the action of a flow of a work fluid of centrifugal radial type, i.e. mainly directed from the rotation axis “X-X” towards the outside.

The first support disc 3 has a second face 21, opposite the first 9, which bears two annular appendices (or reliefs) 22. As is visible in FIG. 3, the annular appendices 22 form concentric rings coaxial with the rotation axis “X-X”.

Also the second support disc 4 has a second face 23, opposite the first 15, which bears two annular appendices (or reliefs) 24. Analogous to the first support disc 3, the annular appendices 24 of the second support disc 4 form concentric rings coaxial with the rotation axis “X-X”.

The first and the second rotation shaft 5, 6 are aligned along the common rotation axis “X-X” and are each extended from the second face 21, 23 of the respective support disc 3, 4 along opposite directions.

The first support disc 3 has, in a zone radially internal with respect to the radial rotor stages 10, 11, 12, 13 and radially external with respect to its rotation shaft 5, through induction channels 25 which traverse the thickness of the first support disc 3 along a substantially axial direction and are opened both on the first face 9 and on the second face 15.

As is visible in FIG. 3, said through induction channels 25 are arranged along a circular path coaxial with the rotation axis “X-X” and are delimited by radially opposite portions of the first support disc 3 and by a plurality of induction rotor blades 26 which form an axial rotor stage 27. In other words, the axial rotor stage 27 is defined by a circular opening which is extended along the abovementioned circular path, within which the induction rotor blades 26 are placed which connect radially opposite portions of the first support disc 3.

The second support disc 4 has, in a radially internal zone with respect to the radial rotor stages 16, 17, 18, 19 and radially external zone with respect to its rotation shaft 7, through induction channels 28 which cross through the thickness of the second support disc 4 along a substantially axial direction and are opened both on the first face 15 and on the second face 23.

In a manner structurally identical to the first support disc 3, said through induction channels 28 are arranged along a circular path coaxial with the rotation axis “X-X” and are delimited by radially opposite portions of the second support disc 4 and by a plurality of induction rotor blades 29 which form an axial rotor stage 30. In other words, the axial rotor stage 30 is defined by a circular opening that is extended along the abovementioned circular path, within which the induction rotor blades 29 are placed which connect radially opposite portions of the second support disc 4.

The two discs 3, 4, including the induction rotor blades 26, 29, are preferably made in a single piece, e.g. by means of three-dimensional sintering techniques.

The leading edge and the trailing edge of each of the abovementioned blades 26, 29 of the axial rotor stages 27, 30 are extended substantially radially (along radial directions with respect to said rotation axis “X-X”), so that they are capable of working under the action of a flow of the work fluid of axial type, i.e. mainly directed parallel to the rotation axis “X-X”. The leading edge of each of the induction blades 26, 29 faces the second face 21, 23 of the respective disc 3, 4 and the trailing edge faces the first face 9, 15 of the respective disc 3, 4.

The two first faces 9, 15 together delimit an expansion volume 31 of the work fluid which enters into said expansion volume 31 through the through induction channels 25, 28 of the two support discs 3, 4 and is radially expanded away from the rotation axis “X-X” through the radial rotor stages 10, 11, 12, 13, 16, 17, 18, 19 of said two discs 3, 4 and exits at a radially peripheral portion of the abovementioned discs 3, 4.

The orientation of the blades 14 of the radial rotor stages 10, 11, 12, 13 of the first disc 3 is opposite the orientation of the blades 20 of the radial rotor stages 16, 17, 18, 19 of the second disc 4, so that the expansion of the work fluid causes the rotation in opposite senses of said two discs 3, 4.

Preferably, the ratio between the radial height of each induction rotor blade 26, 29 and the diameter of the support discs 3, 4 is comprised between about 0.007 and about 0.050. In the illustrated embodiment, such ratio is for example equal to about 0.025.

The expansion turbine 1 also comprises a first portion 32 that is fixed (with respect to the containment case 2) provided with a plurality of fixed induction openings 33 axially side-by-side the induction rotor blades 26 of the first support disc 3 and placed on the side of the second face 21 of said first disc 3. The first fixed portion 32 can be an integral part of the case 2 or stably mounted in the case 2. As is visible in FIG. 4, the first fixed portion 32 has an annular passage coaxial with the rotation axis “X-X” and a plurality of stator blades 34, situated in said annular passage, divide it into the abovementioned fixed induction openings 33. The stator blades 34 are extended substantially radially (along radial directions with respect to said rotation axis “X-X”). The stator blades 34 form an axial stator stage 35 which together with the respective axial rotor stage 27 define an axial induction stage for the first support disc 3.

A second fixed portion 36 flanks the second face 23 of the second support disc 4. The second fixed portion 36 is provided with a plurality of fixed induction openings 37 axially side-by-side the induction rotor blades 29 of the second support disc 4. The second fixed portion 36 can be an integral part of the case 2 or stably mounted in the case 2. Analogous to the first fixed portion 32, the second fixed portion 36 has an annular passage coaxial with the rotation axis “X-X” and a plurality of stator blades 38, situated in said annular passage, divide it into the abovementioned fixed induction openings 37. The stator blades 38 are extended substantially radially (along radial directions with respect to said rotation axis “X-X”). The stator blades 38 form an axial stator stage 39 which together with the respective axial rotor stage 30 define an axial induction stage for the second support disc 4.

The first fixed portion 32 is radially extended away from the rotation axis “X-X” (like a fixed disc) and has a respective face 40 placed across the annular appendices 22 of the first support disc 3. From said face 40 of the first fixed portion 32, two annular walls 41 coaxial with the rotation axis “X-X” (see FIG. 4) are extended. Each annular wall 41 is axially extended nearly to the second face 21 of the first support disc 3 at a respective annular appendage 22.

As is better visible in the detail of FIG. 5, the annular appendage 22 remains arranged in a radially more internal position with respect to the respective annular wall 41. An end 42 of the annular wall 41 lies in proximity to the annular appendage 22 and bears a sliding gasket 43 which remains radially interposed between said end 42 and said annular appendage 22. The sliding gasket 43 lies in contact with and slides on the annular appendage 22, ensuring the seal of the work fluid.

The radially successive annular walls 41 delimit, together with the face 40 of the first fixed portion 32 and the second face 21 of the first support disc 3, a first annular chamber 44.

The second fixed portion 36 is structurally similar to the first fixed portion 32. A respective face 46 is placed across from the annular appendices 24 of the second support disc 4. From said face 46, two annular walls 47 are extended (as much as the annular appendices 24) coaxial with the rotation axis “X-X”. Each annular wall 47 is axially extended up to nearly the second face 23 of the second support disc 4 at a respective annular appendage 24.

The annular appendage 24 remains arranged in a radially more internal position with respect to the respective annular wall 47. In mirrored manner with respect to that represented in FIG. 5, one end 42 of the annular wall 47 lies in proximity to the annular appendage 24 and bears a sliding gasket 43 which remains radially interposed between said end 42 and said annular appendage 24. The sliding gasket 43 lies in contact with and slides on the annular appendage 24, ensuring the seal of the work fluid.

The radially successive annular walls 47 delimit, together with the face 46 of the first fixed portion 36 and the second face 23 of the second support disc 4, a second annular chamber 48.

In the illustrated embodiment, both the first and the second fixed portion 32, 36 have a hole 50 for the passage of the respective rotation shaft 5, 7 (FIG. 4).

In addition, both the support discs 3, 4 have compensation through openings 52 obtained in radially internal positions with respect to the through induction channels 25, 28.

The illustrated turbine 1 also comprises two auxiliary axial stages 53, each situated at a zone radially external with respect to the respective support disc 3, 4. Hereinbelow reference is only made to one of said stages 53, since these are structurally identical.

The auxiliary axial stage 53 comprises a plurality of auxiliary rotor blades 54 mounted on a peripheral edge of the respective support disc 3, 4 and a plurality of auxiliary stator blades 55 mounted on a support element 2 a making up part of a radially external portion of the containment case 2 and placed in a radially external position with respect to the support disc 3, 4.

The auxiliary rotor blades 54 are radially extended from the peripheral edge of the respective disc 3, 4 towards the outside, as is visible in FIG. 3. The auxiliary stator blades 55 are radially extended from the support element 56 and converge towards the rotation axis “X-X”.

Radially internal terminal ends of the auxiliary stator blades 55 are borne by a radially internal ring 56. Such ring 56 is situated at the peripheral edge of the respective support disc 3, 4 and faces the first face 9, 15 of said disc 3, 4.

Each of the support discs 3, 4 has an auxiliary annular appendage 57 projecting from the respective first face 9, 15, coaxial with the rotation axis “X-X” and placed in a position radially external with respect to the radial rotor stages 10-13, 16-19. The radially internal ring 56 lies in a position that is radially external with respect to the auxiliary annular appendage 57 and in proximity to said auxiliary annular appendage 57 and bears a sliding gasket that remains radially interposed between said internal ring 56 and said auxiliary annular appendage 57. The sliding gasket lies in contact with and slides on the auxiliary annular appendage 57, ensuring the seal of the work fluid.

The containment case 2 delimits a first induction chamber 58 arranged on one side of the first fixed portion 32 opposite the respective first support disc 3. The first induction chamber 58 is annular and faces and is in fluid communication with the fixed induction openings 33 of the first fixed portion 32. The first induction chamber 58 is also in fluid communication with a source 59 of work fluid (e.g. a circuit placed upstream of the turbine 1) intended to be expanded in the turbine 1.

The containment case 2 delimits a second induction chamber 60 arranged on one side of the second fixed portion 36 opposite the respective second support disc 4. The second induction chamber 60 is annular and faces and is in fluid communication with the fixed induction openings 37 of the second fixed portion 36. The second induction chamber 60 is in fluid communication with the source 59 of work fluid intended to be expanded in the turbine 1.

During use, the work fluid coming from the source 59 enters into the induction chambers 58, 60 through suitable ducts 61 and from these flows axially through the fixed induction openings 33, 37, the stator blades 34, 38 of the fixed portions 32, 36 and through the induction rotor blades 26, 29 of the support discs 3, 4. The speed of the work fluid through the induction channels 25, 28 is for example comprised between about 40 m/s and about 45 m/s.

The work fluid then flows through the radial rotor stages 10-13, 16-19 of the first and of the second disc 3, 4 and subsequently through the auxiliary axial stages 53. The work fluid exiting from the auxiliary axial stage 53 is then conveyed into a volume 62 (preferably a volute) delimited by the containment case 2 towards a circuit placed downstream of the turbine 1.

The embodiment illustrated in FIG. 2 has only one support disc 3. Elements analogous to those illustrated and described for the counter-rotating turbine of FIG. 1 will not be described again in detail herein; for the sake of simplicity, the same reference numbers are used for these elements.

The support disc 3 has a first face 9 which bears a plurality of radial rotor stages 10, 11, 12 radially arranged in succession one after the other.

Across from the first face 9, a wall 63 of the containment case 2 is placed that bears a plurality of radial stator stages 64, 65 arranged radially in succession one after the other. Each of the stator stages 64, 65 comprises an array of blades 66 arranged in succession along a respective circular path. The stator stages 64, 65 are radially alternated with the rotor stages 10, 11, 12.

The expansion volume 31 is delimited in this embodiment between the support disc 3 and the wall 63 of the containment case 2.

The structure of the single support disc 3 is substantially the same as the first support disc 3 described and illustrated for the counter-rotating turbine of FIG. 1.

Analogous to the counter-rotating turbine of FIG. 1, the turbine of FIG. 2 has two annular walls 41 having ends 42 lying in proximity to annular appendices 22 extended from the second face 21 of the support disc 3 in order to delimit an annular chamber 44.

Analogous to the counter-rotating turbine of FIG. 1, also the turbine of FIG. 2 comprises an auxiliary axial stage 53 comprising a plurality of auxiliary rotor blades 54 mounted on a peripheral edge of the support disc 3 and a plurality of auxiliary stator blades 55 mounted fixed on a support element 56 making up part of a radially external portion of the containment case 2.

Analogous to the counter-rotating turbine of FIG. 1, also the turbine of FIG. 2 comprises the induction channels 25 obtained in the support disc 3 and provided with induction rotor blades 26 defining the axial rotor stage 27.

Analogous to the counter-rotating turbine of FIG. 1, also the turbine of FIG. 2 comprises the fixed induction openings 33 axially side-by-side the induction rotor blades 26 of the support disc 3 and placed on the side of the second face 21 of said disc 3. The fixed induction openings 33 have the induction stator blades 34 defining the axial stator stage 35.

Unlike the counter-rotating turbine of FIG. 1, the turbine of FIG. 2 comprises a nose 67 (e.g. a kind of pointed element) coaxial with the rotation axis “X-X” and situated on the side of the second face 21 of the support disc 3. The nose 67 peripherally bears the induction stator blades 34 and is directed towards an axial inlet 68. The nose 67 deflects the flow entering from the axial inlet 68 towards the fixed induction openings 33 that surround it. 

1. Centrifugal radial turbine, comprising: a fixed containment case (2); at least one support disc (3, 4) having a first face (9, 15) bearing at least one radial rotor stage (10, 11, 12, 13, 16, 17, 18, 19) formed by an array of blades (14, 20) arranged in succession along a respective circular path; and at least one rotation shaft (5, 7) integral with the respective disc (3, 4); wherein said at least one radial rotor stage (10, 11, 12, 13, 16, 17, 18, 19) is situated in an expansion volume (31) for a work fluid, wherein said at least one disc (3, 4) has through induction channels (25, 28) situated in radially external position with respect to the respective shaft (5, 7) and radially internal position with respect to said at least one radial rotor stage (10, 11, 12, 13, 16, 17, 18, 19), wherein said at least one disc (3, 4) is free to rotate together with the respective shaft (5, 7) around a rotation axis (X-X) under the action of the work fluid entering through the through induction channels (25, 28), and wherein, at the respective through induction channels (25, 28), said at least one disc (3, 4) comprises a plurality of induction rotor blades (26, 29) of at least one respective axial rotor stage (27, 30).
 2. The turbine according to claim 1, wherein the induction channels (25, 28) are at least partially delimited by said induction rotor blades (26, 29).
 3. The turbine according to claim 1, wherein the induction rotor blades (26, 29) are integrally obtained in said at least one support disc (3, 4).
 4. The turbine according to 1, wherein the ratio between the radial height of each induction rotor blade (26, 29) and the diameter of said at least one support disc (3, 4) is comprised between about 0.007 and about 0.05.
 5. The turbine according to claim 1, wherein an axial traversing speed of the work fluid through the induction channels (25, 28) is comprised between about 35 m/s and about 100 m/s, preferably between about 40 m/s and about 45 m/s.
 6. The turbine according to claim 1, further comprising a plurality of induction stator blades (34, 38) of the respective axial stage (27, 35, 30, 39) side-by-side the induction rotor blades (26, 29) of said at least one support disc (3, 4) and placed to the side of a second face (21, 23) of the respective support disc (3, 4) opposite the first face (9, 15).
 7. The turbine according to claim 1, further comprising at least one radial stator stage (63, 66) fixed with respect to the containment case (2) and formed by an array of blades (66) arranged in succession along a respective circular path and in radially external and/or radially internal position with respect to said at least one radial rotor stage (10, 11, 12), wherein the expansion volume (31) is delimited between the support disc (3) and the containment case (2).
 8. The turbine according to claim 7, further comprising a nose (67) integral with the containment case (2), placed on the side of a second face (21) of the support disc (3) opposite the first face (9) and situated in an inlet duct (68).
 9. The turbine according to claim 1, further comprising: a plurality of induction stator blades (34, 38) of the respective axial stage (27, 35, 30, 39) side-by-side the induction rotor blades (26, 29) of said at least one support disc (3, 4) and placed to the side of a second face (21, 23) of the respective support disc (3, 4) opposite the first face (9, 15); at least one radial stator stage (63, 66) fixed with respect to the containment case (2) and formed by an array of blades (66) arranged in succession along a respective circular path and in radially external and/or radially internal position with respect to said at least one radial rotor stage (10, 11, 12), wherein the expansion volume (31) is delimited between the support disc (3) and the containment case (2); and a nose (67) integral with the containment case (2), placed on the side of a second face (21) of the support disc (3) opposite the first face (9) and situated in an inlet duct (68), wherein the induction stator blades (34) are situated circumferentially around the nose (67).
 10. The turbine according to claim 1, wherein said turbine is of counter-rotating type and comprises a first support disc (3) and a second support disc (4), wherein the first disc (3) faces the second disc (4) in order to delimit the expansion volume (31) and the blades (14) of the first disc (3) are radially alternated with the blades (20) of the second disc (4).
 11. The turbine according to claim 1, wherein the axial rotor stage (27, 30) is of action type.
 12. The turbine according to claim 1, wherein the axial rotor stage (27, 30) is of reaction type.
 13. The turbine according to claim 1, wherein the support disc or discs (3, 4) have compensation through openings (52) obtained in radially internal positions with respect to the through induction channels (25, 28), in order to balance the axial thrust on the discs (3, 4).
 14. The turbine according to claim 1, further comprising an annular chamber (44, 48) that is concentric and facing the second face of the support disc or of each support disc (3, 4); wherein the fixed containment case (2) which houses the support disc or discs (3, 4) comprises annular walls (41, 47) coaxial with the rotation axis (X-X) and delimiting said annular chamber(s) (44, 48).
 15. Apparatus for generating mechanical and/or electrical energy comprising a turbine according to claim
 1. 